Early bowling balls were provided with two cylindrical holes: one for the thumb and the other for the middle finger. Later, because of difficulty in holding the weight of the ball and also to obtain better control during the delivery there came into general use a ball with three cylindrical holes: one for the thumb and the other two for the middle and ring fingers. Typically, the middle and ring finger holes are spaced from the thumb hole a sufficient distance to allow the ball to be held firmly, but comfortably, with the first and second phalanges completely inserted therein. In a three-hole ball, the middle and ring finger holes are in close proximity to each other to permit gripping of the ball without hand distortion. The ball is thus held by reason of a clamping action exerted by the thumb and the fingers in addition to the friction between the sides of the holes and the fingers.
While the three-fingered ball is in most common use today, primarily due to the relatively high standard weight of bowling balls, it is generally considered that the two-hole ball produces a more accurate delivery. This is due primarily to the difficulty of coordinating the two middle fingers so that they will release the bowling ball simultaneously. A small difference in the time of release by the two middle fingers significantly affects the ball trajectory resulting in a loss of accuracy.
To achieve a high degree of proficiency in the sport of bowling, it is essential that the ball properly and comfortably fit the hand and fingers of the individual bowler (particularly when a three-hole ball is used). The fit around the thumb should be just loose enough for comfort yet tight enough to maintain a frictional grip when the thumb is bent at the joint and removed from the hole upon delivery of the ball. The holes for the other fingers should fit with the same degree of looseness. When the holes are too small, the fingers soon become irritated, torn and scraped because the fingers have a tendency to expand after a few balls have been thrown. When the holes are too large, it is difficult to hold the ball properly possibly resulting in the ball slipping out of the bowler's hand prematurely during the delivery.
To eliminate the tendency for the ball to leave the bowler's hand prematurely, various expediences have been proposed such as the use of chalk and other sticky material and the provision of liners for the holes made of compressible and yieldable material such as cork, soft rubber or another resilient material. It has also been suggested to corrugate the inside surfaces of the holes, to otherwise roughen the wall surfaces, and to provide inserted hard liners having rough areas. While these techniques can provide a certain degree of friction for gripping purposes, they tend to cause abrasion and soreness of the fingers.
The most common means for fitting a bowling ball involves the use of a spherical assembly having two sections rotatable relative to each other, each section including numerous holes for insertion of the thumb and bowling fingers. The bowler inserts each of his bowling fingers and thumb into the various holes until he selects those which appear to have a proper degree of clearance, or from which the optimum hole diameter may be estimated. Having done so, he then reinserts his thumb into the hole most closely approximating his optimum size, and rotates the opposite section of the assembly until he locates two adjacent finger holes thereon most closely approximating a comfortable span for his hand, the finger span being measured from the base of the thumb. The selected ball is then drilled to those span and hole diameter specifications. The slightest error in either the finger span measurements or the drilling of the finger holes adversely affects the performance of the bowler in a significant way.
Errors in the measuring or drilling process result in an unequal distribution of the load upon the fingers. In due course an overloaded finger may suffer serious finger strain or a more severe injury such as a torn ligament. In addition to finger injury, inaccurately measured finger spans and imprecisely drilled holes cause the fingers to lift different loads. These differing loads make it very difficult, if not impossible, to extract the fingers from the holes simultaneously as is desired to obtain the most accuracy.
Another consequence of drilling separate finger holes designed to match the differing finger sizes and spans of the middle and ring fingers is that the "pitch" of each finger hole may be different. "Pitch" is defined as the angular and linear differences of the longitudinal axis of a hole or cavity with respect to the center of the ball. When the "pitch" of each finger hole is different, the lifting leverage of each finger can be different with respect to the other, thereby causing non-uniform forces to be directed toward the thumb hole and resulting in an inaccurate delivery.
Various methods and devices designed to remedy the aforementioned problems have been proposed over the years, and examples can be found in U.S. Pat. Nos. 2,274,522; 2,347,771; 2,482,190; 2,991,079; 3,329,429, 3,454,440; and 4,150,822. Nevertheless, satisfactory ball constructions which take into account the different finger spans of the individual fingers, remedy the problems presented by different "pitches" of the finger holes, and eliminate unequal load distribution between the lifting fingers in order to insure the simultaneous release of the lifting fingers and the accurate delivery of the bowling ball have not been found.
Accordingly, there is a need to alter and control the individual lifting forces originating from separate and distinct points and, so far as possible, merge these forces into a single lifting force predictably directed from the lifting edge of the finger holes toward the thumb. Additionally, it is desirable that a device be provided which allows for as much flexibility and utility in the use of a single ball as is practicable. For example, a single ball which provided a finger-tip grip as well as a conventional grip, each with its own performance characteristics, would be desirable for the bowler interested in obtaining the different performances of two balls in one. Finally, there is also a need for a gripping arrangement which enhances the bowler's control and comfort by accounting for differing finger spans, remedying "pitch" difference problems, and eliminating unequal load distributions.